
theorem
  for R being RelStr, T1 being TopAugmentation of R
  for T2 being TopAugmentation of T1 holds T2 is TopAugmentation of R
proof
  let R be RelStr, T1 be TopAugmentation of R;
  let T2 be TopAugmentation of T1;
  thus the RelStr of T2 = the RelStr of T1 by Def4
    .= the RelStr of R by Def4;
end;
